In conventional technologies of solar energy, sheets of boron-doped monocrystalline silicon are generally used as the substrate materials for manufacturing solar cells. The doping process of such boron-doped monocrystalline silicon material is convenient and easy to be made, and the resistivity distribution of the produced monocrystalline silicon rod is uniform.
However, the cell efficiency of the solar cell, which is manufactured by using the boron-doped monocrystalline silicon, in particular the boron-doped monocrystalline silicon with low resistivity ranging from 0.5 to 1.5 Ω-CM, as the substrate material, will degrade with sunlight or carriers injection. Such phenomenon is referred to as Light Induced Degradation (LID).
At present, the degradation in efficiency of the commercial boron-doped monocrystalline silicon solar cell in the market is approximately 3% to 7%. The essential reason for such characteristic of LID in cell efficiency is that, since the substitutional boron atom in the boron-doped monocrystalline silicon and the oxygen atom in the gap state in the monocrystalline silicon will form a complex of boron and oxygen with sunlight or carriers injection, wherein the complex of boron and oxygen is the deep level recombination centre, the life of a minority carriers will be reduced, and thus the diffusion length of the minority carriers will be decreased, resulting in the reduced efficiency of the solar cell. The LID will be particularly noticeable under the condition of the market shortages in the silicon materials and uneven in quality of the silicon materials.